A 26-year-old man was shot in the head and critically hurt outside a nightclub in north-west London, police have said.
The victim was attacked near the Jet Set club in High Street, Harlesden, at about 0500 GMT on Sunday.
Scotland Yard said the man and a friend had become involved in an argument with another man close to the club.
The pair walked away but were followed by the man who produced a gun and fired. The second man, aged 22, was struck over the head and slightly hurt.
The shooting victim was being treated in a north London hospital. A Metropolitan Police spokesman said: "It is believed there were around 15 bystanders in the vicinity at the time of the shooting.
"We are specifically appealing for any of these people who have not yet spoken to police to come forward."